Arterial Blood Pressure Pulse Research Articles

Changes in autonomic function and cerebral and somatic oxygenation with arterial flow pulsatility for children requiring veno-arterial extracorporeal membrane oxygenation

BackgroundVeno-arterial extracorporeal membrane oxygenation (VA-ECMO) carries variability in arterial flow pulsatility (AFP). Research questionWhat changes in cerebral and somatic oxygenation, hemodynamics, and autonomic function are associated with AFP during VA-ECMO? MethodsThis is a prospective study of children on VA-ECMO undergoing neuromonitoring. AFP was quantified by arterial blood pressure pulse amplitude and subcategorized: no pulsatility (<1 mmHg), minimal pulsatility (1 to <5 mmHg), moderate pulsatility (5 to <15 mmHg) and high pulsatility (≥15 mmHg). CVPR was assessed using the cerebral oximetry index (COx). Cerebral and somatic oxygenation was assessed using cerebral regional oximetry (rSO2) or peripheral oxygen saturation (SpO2). Autonomic function was assessed using baroreflex sensitivity (BRs), low-frequency high-frequency (LF/HF) ratio and standard deviation of heart rate R–R intervals (HRsd). Differences were assessed across AFP categories using linear mixed effects models with Tukey pairwise comparisons. Univariate logistic regression was used to explore risk of AFP with brain injuries. ResultsAmong fifty-three children, comparisons of moderate to high pulsatility were associated with reductions in rSO2 (p < 0.001), SpO 2 (p = 0.005), LF/HF ratio (p = 0.028) and an increase in HRsd (p < 0.001). Reductions in BRs were observed across comparisons of none to minimal (P < 0.001) and minimal to moderate pulsatility (p = 0.004). Comparisons of no to low pulsatility were associated with reductions in BRs (p < 0.001) and ABP (p < 0.001) with increases in SpO2 (p < 0.001) and HR (p < 0.001). Arterial ischemic stroke was associated with higher pulsatility (p = 0.0384). ConclusionDuring VA-ECMO support, changes toward high AFP are associated with autonomic dysregulation and compromised cerebral and somatic tissue oxygenation.

A quantitative model of the cerebral windkessel and its relevance to disorders of intracranial dynamics.

Traditional models of intracranial dynamics fail to capture several important features of the intracranial pressure (ICP) pulse. Experiments show that, at a local amplitude minimum, the ICP pulse normally precedes the arterial blood pressure (ABP) pulse, and the cranium is a band-stop filter centered at the heart rate for the ICP pulse with respect to the ABP pulse, which is the cerebral windkessel mechanism. These observations are inconsistent with existing pressure-volume models. To explore these issues, the authors modeled the ABP and ICP pulses by using a simple electrical tank circuit, and they compared the dynamics of the circuit to physiological data from dogs by using autoregressive with exogenous inputs (ARX) modeling. The authors' ARX analysis showed close agreement between the circuit and pulse suppression in the canine cranium, and they used the analogy between the circuit and the cranium to examine the dynamics that underlie this pulse suppression. This correspondence between physiological data and circuit dynamics suggests that the cerebral windkessel consists of the rhythmic motion of the brain parenchyma and CSF that continuously opposes systolic and diastolic blood flow. Such motion has been documented with flow-sensitive MRI. In thermodynamic terms, the direct current (DC) power of cerebral arterial perfusion drives smooth capillary flow and alternating current (AC) power shunts pulsatile energy through the CSF to the veins. This suggests that hydrocephalus and related disorders are disorders of CSF path impedance. Obstructive hydrocephalus is the consequence of high CSF path impedance due to high resistance. Normal pressure hydrocephalus (NPH) is the consequence of high CSF path impedance due to low inertance and high compliance. Low-pressure hydrocephalus is the consequence of high CSF path impedance due to high resistance and high compliance. Ventriculomegaly is an adaptive physiological response that increases CSF path volume and thereby reduces CSF path resistance and impedance. Pseudotumor cerebri is the consequence of high DC power with normal CSF path impedance. CSF diversion by shunting is an accessory windkessel-it drains energy (and thereby lowers ICP) and lowers CSF path resistance and impedance. Cushing's reflex is an accessory windkessel in extremis-it maintains DC power (arterial hypertension) and reduces AC power (bradycardia). The windkessel theory is a thermodynamic approach to the study of energy flow through the cranium, and it points to a new understanding of hydrocephalus and related disorders.

Why don't ventricles dilate in pseudotumor cerebri? A circuit model of the cerebral windkessel.

Pseudotumor cerebri is a disorder of intracranial dynamics characterized by elevated intracranial pressure (ICP) and chronic cerebral venous hypertension without structural abnormalities. A perplexing feature of pseudotumor is the absence of the ventriculomegaly found in obstructive hydrocephalus, although both diseases are associated with increased resistance to cerebrospinal fluid (CSF) resorption. Traditionally, the pathophysiology of ventricular dilation and obstructive hydrocephalus has been attributed to the backup of CSF due to impaired absorption, and it is unclear why backup of CSF with resulting ventriculomegaly would not occur in pseudotumor. In this study, the authors used an electrical circuit model to simulate the cerebral windkessel effect and explain the presence of ventriculomegaly in obstructive hydrocephalus but not in pseudotumor cerebri. The cerebral windkessel is a band-stop filter that dampens the arterial blood pressure pulse in the cranium. The authors used a tank circuit with parallel inductance and capacitance to model the windkessel. The authors distinguished the smooth flow of blood and CSF and the pulsatile flow of blood and CSF by using direct current (DC) and alternating current (AC) sources, respectively. The authors measured the dampening notch from ABP to ICP as the band-stop filter of the windkessel. In obstructive hydrocephalus, loss of CSF pathway volume impaired the flow of AC power in the cranium and caused windkessel impairment, to which ventriculomegaly is an adaptation. In pseudotumor, venous hypertension affected DC power flow in the capillaries but did not affect AC power or the windkessel, therefore obviating the need for adaptive ventriculomegaly. In pseudotumor, the CSF spaces are unaffected and the windkessel remains effective. Therefore, ventricles remain normal in size. In hydrocephalus, the windkessel, which depends on the flow of AC power in patent CSF spaces, is impaired, and the ventricles dilate as an adaptive process to restore CSF pathway volume. The windkessel model explains both ventriculomegaly in obstructive hydrocephalus and the lack of ventriculomegaly in pseudotumor. This model provides a novel understanding of the pathophysiology of disorders of CSF dynamics and has significant implications in clinical management.

194 Why Do Ventricles Not Dilate in Pseudotumor Cerebri? A Circuit Model of Cerebral Windkessel

INTRODUCTION: Pseudotumor cerebri is characterized by elevated intracranial pressure (ICP) without ventricular dilation. The pathophysiology of pseudotumor is traditionally viewed as chronic cerebrovenous hypertension which causes impaired cerebrospinal fluid (CSF) resorption. Increased resistance to CSF absorption results in ventriculomegaly in obstructive hydrocephalus. In pseudotumor, however, lack of ventriculomegaly cannot be explained by this mechanism. In this study, we model the cerebral windkessel as a CSF pulsation absorber. We hypothesize that inability to absorb CSF pulsation diverts pulsatile energy to ventricles, causing ventriculomegaly, whereas effective CSF pulsation absorption leaves ventricles normal in size. METHODS: Cerebral windkessel is a band-pass filter considering arterial blood pressure (ABP) as input and ICP as output. We used a tank circuit with parallel inductance and capacitance to model windkessel and compare with the transfer function between ABP and ICP in normal dogs. Normal CSF dynamics were simulated by setting circuit parameters to correlate physiological recordings from dogs: frequency for heart rate, input and output voltages for ABP and ICP, and CSF and capillary resistance for resistance to pulsatile and pulseless flow, respectively. CSF path resistance was increased to simulate CSF space narrowing in hydrocephalus. Capillary resistance was increased to simulate impaired venous flow in pseudotumor. RESULTS: The circuit output shows agreement with physiological recordings, in which ICP pulse precedes ABP pulse. Windkessel is most effective at a given pulse frequency. In hydrocephalus, increased resistance to CSF flow disrupts cerebral windkessel, leading to ineffective pulse dampening and increased ICP phase lead. In pseudotumor, increased capillary resistance does not change cerebral windkessel effectiveness or ICP phase lead. CONCLUSION: The cerebral windkessel is a CSF pulsation absorber. An ineffective windkessel in hydrocephalus inhibits CSF pulsation absorption and diverts pulsatile energy to dilate ventricles, whereas an effective one in pseudotumor leaves ventricles normal. Our model of CSF dynamics emphasizes that ventricular dilation is a result of ineffective windkessel and decreased CSF pulsation absorption. This model provides a novel perspective on the pathophysiology of abnormal CSF dynamics and offers new directions for future research.

Recognition of dicrotic notch in arterial blood pressure pulses using signal processing techniques

The Physiological condition of cardiovascular system is analyzed by arterial blood pressure pulse wave. The arterial pulse wave displays the genetic traits of the heart, average records of a heartbeat and variation in pressure as the heart spouts blood. This pulse monitoringis a standard process used to assess the cardiovascular system’s medical history. A waveform ofthe Arterial blood pressure usually involves a systolic level, diastolic occurrence, and dicrotic spike and dicrotic notch. The cardiac cavity contracting and relaxing leads to systolic and diastolic blood pressure respectively. The dicrotic notch which is a drop on the down slope shows systole termination and depicts the aorta closure of successive backward stream. The position of the dicrotic notch throughout the cardiac activity differs as per the duration of aortic closure. Dicrotic notch plays an essential part in sclerosis, occlusion, stenosis, arterial spasm and erythromelalgia diagnostic test. Hence Discrete Wavelet transform is utilized in this proposed work to examine and assess the dicrotic notch in arterial pulse wave form. Arterial pulse data are processed using a data acquisition system consisting of multiple channels sensor signal processing and a computer to collect the necessary data for future examination. The uniform peer group of 22 patients has been evaluated utilizing two distinct Haar and Daubuchies4 (db4) wavelet transformations. The peripheral wave in the patients seems to have a sharp rise and a notch on dropping slope, has been identified. The data collected are contrasted between the two techniques, and the Haar wavelet is observed to reasonably represent the best outcome.

Blood Pressure Morphology Assessment from Photoplethysmogram and Demographic Information Using Deep Learning with Attention Mechanism.

Arterial blood pressure (ABP) is an important vital sign from which it can be extracted valuable information about the subject’s health. After studying its morphology it is possible to diagnose cardiovascular diseases such as hypertension, so ABP routine control is recommended. The most common method of controlling ABP is the cuff-based method, from which it is obtained only the systolic and diastolic blood pressure (SBP and DBP, respectively). This paper proposes a cuff-free method to estimate the morphology of the average ABP pulse () through a deep learning model based on a seq2seq architecture with attention mechanism. It only needs raw photoplethysmogram signals (PPG) from the finger and includes the capacity to integrate both categorical and continuous demographic information (DI). The experiments were performed on more than 1100 subjects from the MIMIC database for which their corresponding age and gender were consulted. Without allowing the use of data from the same subjects to train and test, the mean absolute errors (MAE) were 6.57 ± 0.20 and 14.39 ± 0.42 mmHg for DBP and SBP, respectively. For , R correlation coefficient and the MAE were 0.98 ± 0.001 and 8.89 ± 0.10 mmHg. In summary, this methodology is capable of transforming PPG into an ABP pulse, which obtains better results when DI of the subjects is used, potentially useful in times when wireless devices are becoming more popular.

A Unified Approach for Heart Rate Estimation from Electrocardiogram and Arterial Blood Pressure Pulses

The objective of this manuscript is to propose a unique methodology for heart rate estimation derived from Electrocardiogram (ECG) or arterial blood pressure (abp) signal. This methodology relies on the identification of a signal's fundamental frequency by use of empirical wavelet analysis, followed by peak identification within windows based on pseudo-periodic assumption. The proposed methodology is based on the concept that the most of the cardiovascular signals are quasi-periodic in nature. The proposed technique estimates the fundamental frequency of the signal from its corresponding Fourier spectrum using empirical wavelet transform and then utilizes a search window for locating the peaks in the corresponding signal which identifies the R peaks in ECG or Systolic peaks in blood pressure pulses. This approach was validated on 100 recordings of the computing in cardiology challenge 2014 training data set and performance parameters were compared with methods running only on ECG or ABP signals independently.

Peculiarities of Cardiohemodynamics and its Autonomic Regulation in Elderly People

The study was aimed to the experimental verification of the authors’ hypothesis that in elderly people an endogenous functional mechanism develops during late ontogeny to protect muscle effectors of the cardiovascular system (CVS) against negative effects of excessive activity of the sympathetic nervous system by partial replacement of its neurotransmitter norepinephrine with humoral catecholamines. Experiments were carried out using our original method of arterial piezopulsometry which allows evaluation of cardiohemodynamic parameters, as well as the spectral power of oscillations of VmaxPP and TNN parameters of arterial blood pressure pulse waves caused by regulatory effects of the autonomic nervous and endocrine systems. Such a replacement is assumed to be crucial for raising the metabolic tolerance of the CVS in elderly people to an age-related increase in oxygen deficiency, as well as for reducing the incidence of tachyarrhythmia, stenocardia and other cardiac pathological conditions under the influence of psychoemotional and physical stressors.

The Cerebral Windkessel as a Dynamic Pulsation Absorber

The cerebral windkessel is the suppression of the arterial pulse in the cranium which renders capillary blood flow smooth. Arterial pressure and flow are normally synchronous, and (counterintuitively) the intracranial pressure (ICP) pulse slightly precedes the arterial blood pressure (ABP) pulse. Transfer function analysis of the ABP pulse to the ICP pulse shows a local minimum of amplitude response (a notch) at the heart rate, and abnormal intracranial dynamics attenuates the notch and shifts phase. I propose that these counterintuitive aspects of intracranial pulsatility may be understood by treating the cerebral windkessel as a designed system. On that basis, I here apply principles of reverse-engineering to model the ICP pulse first as a simple harmonic oscillator, then as a forced harmonic oscillator with one or two degrees of freedom. By including a model of the intra- and extra-capillary pathways, I show that ABP-ICP dynamics are characteristic of a dynamic pulsation absorber—a system of vibration suppression widely used in engineering. MRI flow imaging shows that this is accomplished by an arterial-cerebrospinal fluid (CSF)-venous pump. During systole, CSF links arterial expansion to venous compression. During diastole, CSF links venous expansion to arterial relaxation. Arterial pulsations pass through the CSF to the veins, and this transposition of the arterial pulse by venous compression and relaxation provides an elastic force that continuously opposes the radial motion of the capillary walls. This maintains the resonant dynamics necessary for efficient perfusion and the anti-resonant dynamics necessary for capillary protection. Maintenance of anti-resonant dynamics (crucial for preventing cerebral edema and capillary damage) requires a system of autoregulation of intracranial pulsatility, which the cerebral windkessel provides.

Ambulatory blood pressure monitoring changes in hypertensive patients

The aim of the study was to determine the peculiarities of ABPM indices in middle-aged and elderly hypertensive patients depending on the daily BP profile.&#x0D; Material and methods. Indices of ambulatory blood pressure monitoring were identified in 57 middle-aged patients (45-59 years) (group I) and 43 elderly patients (60-74 years) (group II), who underwent two-week in-patient treatment. The control group consisted of 15 patients for every of the surveyed categories (group III - middle-aged and group IV – elderly respectively) matched with basic by age and gender.&#x0D; Results. We have shown that one of the factors that determines the change in hemodynamics in patients with essential hypertension is age, with the age patients experience the decrease in diastolic blood pressure with steadily increased systolic blood pressure, that should be considered in the prescription of antihypertensive treatment. With age, a gradual increase in systolic blood pressure is associated with the increased aortic stiffness, partially with the increase in collagen and the decrease in elastic fibrils and the formation of isolated systolic hypertension. Thus, it is proved that in the formation of isolated hypertension the growth of pulse blood pressure for more than 60 mm Hg is unfavorable in a development of cerebrovascular events. Pulse arterial blood pressure was stronger risk factor than systolic blood pressure and diastolic blood pressure or average arterial pressure in the elderly. Recently, taking into account age characteristics, all three indices were recognized as comparable predictors at the age of 50-59 years as the transitional period, and at the age of 60-79 years diastolic blood pressure adversely affecting the cardiovascular risk, increased pulse blood pressure prognostically above the level of systolic arterial pressure.

Abstract TP490: Analysis of Cerebral Hemodynamics and Interaction of 0.1-hz Oscillations of Hemodynamic Parameters in Postural Orthostatic Tachycardia Syndrome

Background: POTS is defined as heart rate increase of more than 30 beats within the first minutes of standing upright. The aim of this study was to analyze causal connectivity among cerebral hemodynamic changes in head-up tilt test (HUT) of POTS using TCD and Finometer between normal and POTS. Methods: Normal (n=20) and POTS (n=20) were enrolled to monitor the beat-to-beat arterial blood pressure (ABP) using Finometer and Cerebral blood flow velocity (CBFV) in right MCA using TCD. Subjects rested in supine position for 5 min and subjects were abruptly positioned at 80 o from horizontal on a tilt table. Beat-to-Beat ABP pulse intervals (HR) were calculated using foot points of each pulse. We divided HUT into early tilt stage (ETS) and late tilt stage (LTS). We analyzed several variables including ABP, HR, systolic CBFV, critical closing pressure (CrCP) between normal and POTS. To analyze effects of intrinsic spontaneous oscillations known as ‘Mayer waves’, in ABP, CBFV, and HR, the frequency component from 0.06Hz to 0.15Hz was extracted using FIR filter. Then Granger causality was calculated to analyze the changes of causal connectivity of each signal by HUT effects. Results: CrCP during HUT in POTS was significantly larger than normal. Compared with normal, POTS showed significantly increased causal flow of ABP◊HR and HR◊CBFV during ETS and causal flow of CBFV◊ABP during LTS. In paired t-test of state change from supine to ETS, while causal flow of ABP◊CBFV in normal was significantly increased during supine, causal flow of ABP◊CBFV and ABP◊HR in POTS were significantly increased during ETS. In paired t-test of state change from ETS to LTS, while causal flow of HR◊CBFV in normal was significantly increased during ETS, causal flow of ABP◊CBFV and HR◊CBFV in POTS were significantly decreased during LTS. In POTS, causal density of HR◊BP during spine was significantly increased and causal density of HR◊CBFV and BP◊CBFV were significantly decreased during LTS. Discussion: This study showed that increased CrCP during HUT is related with increased coupling of 0.1-Hz oscillations from ABP to HR and from HR to CBFV in POTS. Increased CrCP during HUT may cause the excessive blood pooling and the low effective circulating volume in the central vasculature and can explain symptom of POTS.

Peculiarities of 24 hour ambulatory blood pressure monitoring indices in patients with essential hypertension, stage II of different age groups

The aim of the study was to determine peculiarities of 24 hour ambulatory blood pressure monitoring indices of patients with essential hypertension, stage II of different age groups.&#x0D; Material and methods. Indices of ambulatory blood pressure monitoring were identified in 57 middle-aged patients (45-59 years) (group I) and 43 elderly patients (60-74 years) (group II), who underwent two-week in-patient treatment. The control group consisted of 15 patients for every of the surveyed categories (group III - middle-aged and group IV – elderly respectively) matched with basic by age and gender.&#x0D; Results. We have shown that one of the factors that determines the change in hemodynamics in patients with essential hypertension is age, with the age patients experience the decrease in diastolic blood pressure with steadily increased systolic blood pressure, that should be considered in the prescription of antihypertensive treatment. With age, a gradual increase in systolic blood pressure is associated with the increased aortic stiffness, partially with the increase in collagen and the decrease in elastic fibrils and the formation of isolated systolic hypertension. Thus, it is proved that in the formation of isolated hypertension the growth of pulse blood pressure for more than 60 mm Hg is unfavorable in a development of cerebrovascular events. Pulse arterial blood pressure was stronger risk factor than systolic blood pressure and diastolic blood pressure or average arterial pressure in the elderly. Recently, taking into account age characteristics, all three indices were recognized as comparable predictors at the age of 50-59 years as the transitional period, and at the age of 60-79 years diastolic blood pressure adversely affecting the cardiovascular risk, increased pulse blood pressure prognostically above the level of systolic arterial pressure.

Detection of Onset, Systolic Peak and Dicrotic Notch in Arterial Blood Pressure Pulses

In this paper, we proposed an effective method for detecting fiducial points in arterial blood pressure pulses. An arterial blood pressure pulse normally consists of onset, systolic peak and dicrotic notch. Detection of fiducial points in blood pressure pulses is a critical task and has many potential applications. The proposed method employs empirical wavelet transform for locating the systolic peak and onset of blood pressure pulse. The proposed method first estimates the fundamental frequency of blood pressure pulse using empirical wavelet transform and utilizes the combination of the blood pressure pulse and the estimated frequency for locating onset and systolic peak. For dicrotic notch detection, it utilizes the first-order difference of blood pressure pulse. The algorithm was validated on various open-source databases and was tested on a data set containing 12,230 beats. Two benchmark parameters such as sensitivity and positive predictivity were used for the performance evaluation. The comparison results for accuracy of the detection of systolic peak, onset and dicrotic notch are reported. The proposed method attained a sensitivity and positive predictivity of 99.95% and 99.97%, respectively, for systolic peaks. For onsets, it attained a sensitivity and predictivity of 99.88% and 99.92%, respectively. For dicrotic notches, a sensitivity and positive predictivity of 98.98% and 98.81% were achieved, respectively.

Cerebral Critical Closing Pressure: Is the Multiparameter Model Better Suited to Estimate Physiology of Cerebral Hemodynamics?

Cerebral critical closing pressure (CrCP) is the level of arterial blood pressure (ABP) at which small brain vessels close and blood flow stops. This value is always greater than intracranial pressure (ICP). The difference between CrCP and ICP is explained by the tone of the small cerebral vessels (wall tension). CrCP value is used in several dynamic cerebral autoregulation models. However, the different methods for calculation of CrCP show frequent negative values. These findings are viewed as a methodological limitation. We intended to evaluate CrCP in patients with severe traumatic brain injury (TBI) with a new multiparameter impedance-based model and compare it with results found earlier using a transcranial Doppler (TCD)-ABP pulse waveform-based method. Twelve severe TBI patients hospitalized during September 2005-May 2007. Ten men, mean age 32 years (16-61). Four had decompressive craniectomies (DC); three presented anisocoria. Patients were monitored with TCD cerebral blood flow velocity (FV), invasive ABP, and ICP. Data were acquired at 50Hz with an in-house developed data acquisition system. We compared the earlier studied "first harmonic" method (M1) results with results from a new recently developed (M2) "multiparameter method." M1: In seven patients CrCP values were negative, reaching -150mmHg. M2: All positive values; only one lower than ICP (ICP 60mmHg/ CrCP 57mmHg). There was a significant difference between M1 and M2 values (M1<M2) and between ICP and M2 (M2>ICP). M2 results in positive values of CrCP, higher than ICP, and are physiologically interpretable.

Arterial blood pressure monitoring by active sensors based on heart rate estimation and pulse wave pattern prediction

This paper presents the results of development of a novel method for measuring nonstationary quasi-periodic biomedical signals, in particular, the arterial blood pressure pulse signal. It has been demonstrated that the proposed method for compensation tracing of dynamic signals suggests not only smart, but also active sensors. In connection with this, a major part of the introduction is devoted to expanding the conception of smart sensors to the paradigm of active sensors. Further, following the introduction on the background of the question, a brief description of the functioning principles and some design features of the active sensor developed by us are given. The results of the sensor test and calibration are discussed, and the necessity of its complicated control is substantiated. The remaining part of the paper is devoted to possible ways of development of this control and the way that we have chosen to control the active sensor of arterial blood pressure. The principle of controlling compensation of a pulse pressure based on prediction of pulse wave patterns is discussed and substantiated. The final part is devoted to technical matters of formation of dynamic patterns using multiscale correlation analysis of a current local period of heart contractions.

Changes in Cerebral Partial Oxygen Pressure and Cerebrovascular Reactivity During Intracranial Pressure Plateau Waves.

Plateau waves in intracranial pressure (ICP) are frequently recorded in neuro intensive care and are not yet fully understood. To further investigate this phenomenon, we analyzed partial pressure of cerebral oxygen (pbtO2) and a moving correlation coefficient between ICP and mean arterial blood pressure (ABP), called PRx, along with the cerebral oxygen reactivity index (ORx), which is a moving correlation coefficient between cerebral perfusion pressure (CPP) and pbtO2 in an observational study. We analyzed 55 plateau waves in 20 patients after severe traumatic brain injury. We calculated ABP, ABP pulse amplitude (ampABP), ICP, CPP, pbtO2, heart rate (HR), ICP pulse amplitude (ampICP), PRx, and ORx, before, during, and after each plateau wave. The analysis of variance with Bonferroni post hoc test was used to compare the differences in the variables before, during, and after the plateau wave. We considered all plateau waves, even in the same patient, independent because they are separated by long intervals. We found increases for ICP and ampICP according to our operational definitions for plateau waves. PRx increased significantly (p=0.00026), CPP (p<0.00001) and pbtO2 (p=0.00007) decreased significantly during the plateau waves. ABP, ampABP, and HR remained unchanged. PRx during the plateau was higher than before the onset of wave in 40 cases (73%) with no differences in baseline parameters for those with negative and positive ΔPRx (difference during and after). ORx showed an increase during and a decrease after the plateau waves, however, not statistically significant. PbtO2 overshoot after the wave occurred in 35 times (64%), the mean difference was 4.9±4.6Hg (mean±SD), and we found no difference in baseline parameters between those who overshoot and those who did not overshoot. Arterial blood pressure remains stable in ICP plateau waves, while cerebral autoregulatory indices show distinct changes, which indicate cerebrovascular reactivity impairment at the top of the wave. PbtO2 decreases during the waves and may show a slight overshoot after normalization. We assume that this might be due to different latencies of the cerebral blood flow and oxygen level control mechanisms. Other factors may include baseline conditions, such as pre-plateau wave cerebrovascular reactivity or pbtO2 levels, which differ between studies.

Fatigue influence on dynamics of cardiovas­cular functional parameters during head-­up tilt table test in women non-­athletes cohort

Cardiovascular response to the head-up tilt table test in the period when the vasovagal reaction emerges can reveal important information useful for diagnostic and preventive purposes. The aim of this study was to evaluate the influence of fatigue on the dynamics of functional cardiovascular parameters during the head-up tilt table test in non-athlete women cohort. A group of healthy non-athlete women attending health promotion training took part in the study (n = 20). In order to investigate the effect of post-workload parametric dynamics the subjects performed a 30-minute running sessions at a moderate intensity (aerobic exercising). Electrocardiography (ECG), arterial blood pressure (ABP) measurements were employed for the assessment of cardiovascular changes during an orthostatic test (head-up tilt table test) before and after the training session. The study results revealed significant differences in cardiovascular parameters analysed in this study: heart rate (HR), ST-segment depression, systolic, diastolic and pulse ABP before and after the workload (p

Assessment of functional conditions of basketball and football players during the load by applying the model of integrated evaluation

We consider the human body as an adaptable, complex, and dynamic system capable of organizing itself, though there is none, the only one, factor inside the system capable of doing this job. Making use of the computerized ECG analysis system "Kaunas-load" with parallel registration of ECG carrying out body motor characteristics, ABP, or other processes characterizing hemodynamics enable one to reveal and evaluate the synergistic aspects of essential systems of the human body what particularly extends the possibilities of functional diagnostics. The aim of the study was to determine the features of alterations in the functional condition of basketball and football players and nonathletes during the bicycle ergometry test by applying the model of evaluation of the functional condition of the human body. The study population consisted of 266 healthy athletes and nonathletes. Groups of male basketball players, male football players, male nonathletes, female basketball players, and female nonathletes were studied. A computerized ECG analysis system "Kaunas-load" that is capable of both registering and analyzing the power developed by the subject and 12-lead ECG synchronically were used for evaluating the functional condition of the CVS. The subject did a computer-based bicycle ergometry test. The following ECG parameters at rest and throughout the load - HR, JT interval, and the deduced JT/RR ratio index that reflects the condition between regulatory and supplying systems - were evaluated. After measuring ABP, the pulse amplitude (S-D) was evaluated. The pulse blood pressure ratio amplitude (S-D)/S that depicts the connection between the periphery and regulatory systems was also evaluated. Speeds of changes in physiological parameters during physical load were evaluated too. Heart rate and JT/RR ratio of athletes at the rest and during load were lower, and JT interval of rest was longer and became shorter more slowly during load, compared to that of healthy nonathletes. The pulse arterial blood pressure amplitude of men at rest and during load was higher than that of women. The pulse ABP amplitude of athletes was higher than that of nonathletes. The relative pulse ABP amplitude in the state of rest in the groups of men was higher than in groups of women. The relative pulse amplitude of female basketball players at rest and during load was higher than that of female nonathletes. Significant differences in the dynamics of speed of changes in HR, the pulse ABP amplitude, and the relative pulse ABP amplitude of male and female basketball players, male football players, as well as male and female nonathletes were observed. The newly deduced parameters, namely, speeds of changes in the parameters with changes in the phase of the load reflect very well peculiarities of functional condition of the human body during bicycle ergometry test. The sum total of those newly deduced parameters and customary parameters reveals new functional peculiarities of the human body.

Noninvasive monitoring of elevated intramuscular pressure in a model compartment syndrome via quantitative fascial motion

Compartment syndromes, conditions of elevated intramuscular pressure (IMP) resulting from trauma or chronic overuse, frequently require invasive IMP monitoring for accurate diagnosis. Our objective was to test a noninvasive ultrasound technique for estimating IMP based on fascial displacement waveforms from arterial blood pressure pulses. IMP was increased in the legs of 23 healthy adult subjects up to 80 mmHg using two blood pressure cuffs covering the region from the knee to the ankle. Receiver operator characteristic curves and recursive partitioning were used to determine the sensitivity and specificity of diagnosing elevated IMP using fascial displacement. For one curve, in which several ultrasonic measurement parameters were used along with subject body mass index and blood pressure, the sensitivity and specificity for diagnosing normal IMP (below 30 mmHg) from elevated IMP (30 mmHg and up) was 0.61 and 0.94, respectively. Recursive partitioning, in which IMP was divided into three ranges (normal <30 mmHg, midrange of 30-40 mmHg, and elevated >or=50 mmHg), resulted in improved diagnostic sensitivity (0.77) with almost no change in specificity (0.93).

Interference resistance in automated oscillometric sphygmomanometers

1. Parameters of valid signal in oscillometric methods of measurement of arterial blood pressure depend on values of diastolic and pulse arterial blood pressure, heart rate, type of elasticity and collapse of the humeral artery, volume of the artery, volume of the blood pressure cuff, and the ratio of the duration of arterial pressure oscillations to valid signal period. The peak amplitude of the valid signal varies over a range from 0.31 to 7.34 mm Hg, and heart rate varies from 0.66 to 3.33 Hz. The characteristic point for determining systolic arterial blood pressure is the maximum of the envelope of the “negative” part of oscillometric signals, and for diastolic arterial blood pressure is the maximum rate of the decrease of the envelope of the “positive” part of oscillometric signals. The correlation coefficient between experimental signal and theoretical calculations was found to be 0.84. 2. Two types of interferences, related to breathing and movement of patient, have the largest affect on the results of arterial blood pressure measurements by the oscillometric method. 3. An interference-rejecting algorithm was developed for measuring systolic and diastolic arterial blood pressure. The algorithm was implemented in prototype models of the SA-02 and SA-03 automated sphygmomanometers. Clinical trial of the SA-02 automated sphygmomanometer revealed overall error in determination of systolic and diastolic arterial blood pressure in a sample of 144 patients to beS=6.6 mm Hg for systolic arterial blood pressure andS=6.4 mm Hg for diastolic arterial blood pressure. The results of the trial meet the requirements of the United States standard.